<p> Ocean general circulation models of the IPCC class have biases even when simulating present-day conditions, which may bring into question their predictions of future conditions. This dissertation is about tools for, and results from assessing biases in the Community Earth System Model (CESM) ocean component, by itself and when combined with the Biological Ecosystem Cycling (BEC) model. Newly developed tools and their applications are listed. 1. An offline matrix tracer transport model for the ocean component of CESM. 2. A fast Newton-Krylov implicit tracer equilibrium solver for both the annually-averaged and the seasonally-varying circulation. 3. An effective preconditioner for the solver simulating radiocarbon. Application results: For a natural radiocarbon simulation, an equilibrium solution was obtained in 23 model-years, a dramatic decrease from the 4000 model-years reported for time-stepping. The modeled circulation in the deep Pacific Ocean produced radiocarbon ages twice those of observations. 4. A capability for computing the surface origin of water mass fractions as well as the age of the various water masses. </p><p> Application results: The North Atlantic was the major supplier of ventilated water to not only the Atlantic, but also the Pacific and Indian Oceans. A lack of formation of bottom water in the Southern Ocean was discovered. 5. A capability for restricting the tracer simulation domain to a limited region of the ocean while retaining the effectiveness of advection and diffusion fields on the boundary. This reduces computational costs and allows separating local versus remote impacts of tracer sources on the biogeochemical tracer concentrations. This capability has the potential to provide a platform for further biogeochemical studies. </p><p> Application results: The Indian Ocean region was isolated. Global versus regional circulation effects were determined using radiocarbon. Most of the bias within the region was eliminated by using observational, rather than globally calculated values, on the boundaries. Oxygen production and consumption from a CMIP5 BEC simulation were used to drive a regional oxygen model. Boundary values of oxygen from the CMIP5 BEC simulation were replaced with observations, resulting in less bias within the region. However, significant bias in the location of the Arabian Sea oxygen minimum zone remained.</p>

A quantification of local energy dispersion is employed to distinguish cases of downstream baroclinic development, as described by Orlanski and Sheldon, from among 41 cold-season cyclones that intensified strongly over the eastern North Pacific Ocean. Complete summaries of the eddy energy budget are calculated for each event, and about half are found to be in general accord with the proposed evolution. Almost all of this subset appear to have been influenced by a dispersion of energy from separate cyclones developing over the western North Pacific a day or two earlier. The primary source for eddy energy dispersion downstream and subsequent generation near the eastern cases is a baroclinic conversion associated with ascent in the warm sector of the upstream cyclones. The importance of downstream baroclinic development is confirmed for one eastern North Pacific cyclone in two complementary ways. First, the original eddy energy diagnosis is compared to one based on wave activity. In terms of local group velocity, only minor differences are found during much of the initial evolution. It is only once the tropopause undulations lose their wave-like appearance that the group velocity calculated using eddy energy becomes faster than that depicted by wave activity. Second, by employing numerical simulations, the importance of downstream baroclinic development to the intensification of this cyclone is quantified. Various initial conditions are produced using potential vorticity inversion. Simulations in which an upstream trough/ridge couplet are removed from the initial conditions result in both the absence of a downstream baroclinic development and a weakening of the downstream surface cyclone. The remainder of this study investigates the relationship between cold-season cyclones and sea surface temperature anomalies for small groups of strong cyclones occurring in the western North Pacific region. Previous studies have emphasized the importance of the western ocean boundary currents and their strong sea surface temperature gradients to rapid cyclone development. Physical mechanisms governing this relationship have been studied extensively elsewhere. Here, proxy evidence of systematic changes in the role of surface heat and moisture fluxes during the cold season is presented. Cyclones of similar intensification rates are grouped according to their occurrence either during midwinter or during the early and late cold season. Systematic differences in sea surface temperature anomalies beneath these two groups are interpreted as a proxy for corresponding differences in preconditioning by the upperoceanic mixed layer. Submonthly sea level pressure variations for the same North Pacific cyclones appear to support an interpretation in terms of an upward oceanic influence. It is suggested that the role of preconditioning heat fluxes in cyclones varies because of large-scale seasonal changes in baroclinicity and in the availabilitv of water vapour already in the atmosphere. Similar differences are obtained using a group of strong western North Atlantic cyclones.

Under ice river plume data were collected in the spring of 1988 and 1990 at the mouth of the Great Whale River, Hudson Bay, Canada. Tidal analysis of tide gauge data and predicted tides shows a phase advance and amplitude decrease of the tide under continuous landfast sea ice. Current meter and echosounder measurements, as well as temperature-salinity profiles were taken within the first 2 km off-shore of the river mouth to provide a detailed picture of the nearshore plume conditions. Stable, subcritical flow conditions were observed for most of the sampling period, with the buoyant freshwater plume maintaining a depth of about 4 m almost continuously. During spring low tide (the lowest low tide), the cross-sectional area through which the river discharge must flow decreases substantially, resulting in supercritical (Froude number $>$1) conditions over some periods and the formation of an internal hydraulic jump.

<p> Coral reefs are greatly impacted by the physical characteristics of the water surrounding them. Incidence and severity of mass coral bleaching and mortality events are increasing worldwide due primarily to increased water temperature, but also in response to other stressors. This decline in reef health demands clearer understanding of the compounding effects of multiple stressors, as well as widespread assessment of coral reef health in near-real time.</p><p> Satellites offer a means by which some of the physical stressors on coral reefs can be measured. The synoptic spatial coverage and high repeat sampling frequency of such instruments allow for a quantity of data unattainable by <i> in situ</i> measurements. Unfortunately, errors in cloudmasking algorithms contaminate satellite derived sea surface temperature (SST) measurements, especially during anomalously cold events. Similarly, benthic interference of satellite-derived reflectance signals has resulted in large errors in derivations of water quality or clarity in coral reef environments.</p><p> This work provides solutions to these issues for the coral reef environments of the Florida Keys. Specifically, improved SST cloudmasking algorithms were developed for both Advanced Very High Resolution Radiometer (AVHRR; Appendix A) and Moderate Resolution Imaging Spectroradiometer (MODIS) data (Appendix B). Both of these improved algorithms were used to reveal the extent and severity of a January 2010 cold event that resulted in widespread mortality of Florida Keys corals. Applied to SST data from 2010, the improved MODIS cloudmasking algorithm also showed improved quantity of SST retrievals with minimal sacrifice in data quality.</p><p> Two separate algorithms to derive water clarity from MODIS measurements of optically shallow waters were developed and validated, one focusing on the diffuse downwelling attenuation coefficient (K_d, m^-1) in visible bands (Appendix C), the other on K_d in the ultraviolet (Appendix D). The former utilized a semi-analytical approach to remove bottom influence, modified from an existing algorithm. The latter relied on empirical relationships between an extensive <i>in situ</i> training dataset and variations in MODIS-derived spectral shape, determined using a stepwise principal components regression. Both of these algorithms showed satisfactory validation statistics, and were used to elucidate spatiotemporal patterns of water clarity in the Florida Keys. Finally, an approach was developed to use Landsat data to detect concurrent MODIS-derived reflectance anomalies with over 90% accuracy (Appendix E). Application of this approach to historical Landsat data allowed for long-term, synoptic assessment of the water environment of the Florida Keys ecosystem. Using this approach, shifts in seagrass density, turbidity increases, black water events, and phytoplankton blooms were detected using Landsat data and corroborated with known environmental events.</p><p> Many of these satellite data products were combined with <i>in situ </i> reports of coral bleaching to determine the specific environmental parameters individually and synergistically contributing to coral bleaching. As such, SST and visible light penetration were found to be parsimoniously explaining variance in bleaching intensity, as were the interactions between SST, wind and UV penetration. These relationships were subsequently used to create a predictive model for coral bleaching via canonical analysis of principal coordinates. Leave-one-out-cross-validation indicated that this model predicted `severe bleaching' and `no bleaching' conditions with 64% and 60% classification success, respectively, nearly 3 times greater than that predicted by chance. This model also showed improvement over similar models created using only temperature data, further indicating that satellite assessment of coral bleaching based only on SST data can be improved with other environmental data. Future work should further supplement the environmental parameters considered in this research with databases of other coral stressors, as well as improved quantification of the temperature at the depth of corals, in order to gain a more complete understanding of coral bleaching in response to environmental stress.</p><p> Overall, this dissertation presents five new algorithms to the field of satellite oceanography research. Although validated primarily in the Florida Keys region, most of these algorithms should be directly applicable for use in other coastal environments. Identification of the specific environmental factors contributing to coral bleaching enhances understanding of the interplay between multiple causes of reef decline, while the predictive model for coral bleaching may provide researchers and managers with widespread, near real-time assessments of coral reef health.</p>

Forty years (1958-97) of observed and four simulations of Arctic sea-ice concentration (SIC) data are compared to document and better understand Arctic sea-ice variability. The four simulations result from four different forcings, and they are used in an attempt to quantify the relative importance of thermodynamic and dynamic forcings in the Arctic and its peripheral seas. The four runs (A through D) are forced as follows: Run A is forced with monthly varying monthly mean wind stresses and monthly varying climatological air temperatures, Run B is forced monthly varying monthly mean wind stresses and monthly varying monthly mean air temperatures, Run C is forced with daily varying winds and monthly varying climatological air temperatures and finally, Run D is forced with daily varying winds and monthly varying monthly mean air temperatures. Another goal of this study is to test the ability of the dynamic-thermodynamic sea-ice model used in the simulations to reproduce the observed sea-ice variability. / The dominant mode of anomalous winter (January-March) Arctic sea-ice variability, as determined from EOF analysis, exhibits centres of action in the Greenland and Barents Seas. The time series of this mode has a high winter-to-winter autocorrelation (0.62) and portrays a trend of diminishing ice cover in the above mentioned seas. The dominant mode of the simulated (for all four model runs) winter SIC exhibits a centre of action in the Norwegian-Barents Sea and the associated time series is not statistically significantly correlated to that of the observed. This result is expected as the sea-ice model does not simulate the ocean processes in the Greenland Sea. The dominant mode of simulated anomalous summer (July-September) Arctic seaice variability, as determined from EOF analysis, exhibits variability in all peripheral seas and compares well to previously published observations. The correlation coefficient of the associated time series for observed and simulated results is highest for the model run with a finer dynamical forcing (Run C). Regional time series analysis of area-averaged, anomalous, simulated SIC correlate best with the observed time series when the model is forced with a finer dynamical forcing (Runs C and D) as well, withthe highest correlations occurring in the Beaufort, East Siberian and Laptev Seas. Finally, a comparison of modelled and observed summer mean ice edge variability is presented. The model's ability to reproduce the observed variability in the summer mean ice edge is good and once again, the best comparisons occur when the model is forced with a finer dynamical forcing (Runs C and D) . / Quarante ans (1958-97) d'observations et quatre simulations de la concentration de la glace marine sont comparees pour document er et pour ameliorer notre comprehension de la variabilite de la glace marine de l' Arctique. Les quatres simulations (A aD) avaient pour but de quantifier l'importance relative des for<;ages thermodynamique et dynamique dans l'Arctique et ses mers peripheriques. Vne moyenne mensuelle des vents ainsi qu'une moyenne mensuelle climatologique de la temperature de l'air sont utilisees comme for<;ages dans la simulation A. Pour la simulation B, les for<;ages sont une moyenne mensuelle des vents ainsi qu'une moyenne mensuelle de la temperature de l'air. Les simulations C et D sont forcees avec des valeurs quotidiennes pour les vents. Mais, dans la simulation C une moyenne mensuelle climatologique de la temperature de l'air est utilisee alors qu'une moyenne mensuelle de la temperature de l'air est employee dans la simulation D comme for<;age thermodynamique. Cette etude a aussi pour but de tester la capacite du modele areproduire les observations de la variabilite de la concentration de la glace marine. / Quarante ans (1958-97) d'observations et quatre simulations de la concentration de la glace marine sont comparees pour document er et pour ameliorer notre comprehension de la variabilite de la glace marine de l' Arctique. Les quatres simulations (A aD) avaient pour but de quantifier l'importance relative des for<;ages thermodynamique et dynamique dans l'Arctique et ses mers peripheriques. Vne moyenne mensuelle des vents ainsi qu'une moyenne mensuelle climatologique de la temperature de l'air sont utilisees comme for<;ages dans la simulation A. Pour la simulation B, les for<;ages sont une moyenne mensuelle des vents ainsi qu'une moyenne mensuelle de la temperature de l'air. Les simulations C et D sont forcees avec des valeurs quotidiennes pour les vents. Mais, dans la simulation C une moyenne mensuelle climatologique de la temperature de l'air est utilisee alors qu'une moyenne mensuelle de la temperature de l'air est employee dans la simulation D comme for<;age thermodynamique. Cette etude a aussi pour but de tester la capacite du modele areproduire les observations de la variabilite de la concentration de la glace marine. / Quarante ans (1958-97) d'observations et quatre simulations de la concentration de la glace marine sont comparees pour document er et pour ameliorer notre comprehension de la variabilite de la glace marine de l' Arctique. Les quatres simulations (A aD) avaient pour but de quantifier l'importance relative des for<;ages thermodynamique et dynamique dans l'Arctique et ses mers peripheriques. Vne moyenne mensuelle des vents ainsi qu'une moyenne mensuelle climatologique de la temperature de l'air sont utilisees comme for<;ages dans la simulation A. Pour la simulation B, les for<;ages sont une moyenne mensuelle des vents ainsi qu'une moyenne mensuelle de la temperature de l'air. Les simulations C et D sont forcees avec des valeurs quotidiennes pour les vents. Mais, dans la simulation C une moyenne mensuelle climatologique de la temperature de l'air est utilisee alors qu'une moyenne mensuelle de la temperature de l'air est employee dans la simulation D comme for<;age thermodynamique. Cette etude a aussi pour but de tester la capacite du modele areproduire les observations de la variabilite de la concentration de la glace marine. Quarante ans (1958-97) d'observations et quatre simulations de la concentration de la glace marine sont comparees pour document er et pour ameliorer notre comprehension de la variabilite de la glace marine de l' Arctique. Les quatres simulations (A aD) avaient pour but de quantifier l'importance relative des for<;ages thermodynamique et dynamique dans l'Arctique et ses mers peripheriques. Vne moyenne mensuelle des vents ainsi qu'une moyenne mensuelle climatologique de la temperature de l'air sont utilisees comme for<;ages dans la simulation A. Pour la simulation B, les for<;ages sont une moyenne mensuelle des vents ainsi qu'une moyenne mensuelle de la temperature de l'air. Les simulations C et D sont forcees avec des valeurs quotidiennes pour les vents. Mais, dans la simulation C une moyenne mensuelle climatologique de la temperature de l'air e

This thesis presents the development of a high-resolution viscous-plastic (VP) sea ice model. Because of the fine mesh and the size of the domain, an efficient and parallelizable numerical scheme is desirable. In a first step, we have implemented the nonlinear solver used in existing VP models (referred to as the standard solver). It is based on a linear solver and an outer loop (OL) iteration. For the linear solver, we introduced the preconditioned Generalized Minimum RESidual (pGMRES) method. The preconditioner is a line successive overrelaxation solver (SOR). When compared to the SOR and the line SOR (LSOR) methods, two solvers commonly used in the sea ice modeling community, pGMRES increases the computational efficiency by a factor of 16 and 3 respectively. For pGMRES, the symmetry of the system matrix is not a prerequisite. The Coriolis term and the off-diagonal part of the water drag can then be treated implicitly. Theoretical and simulation results show that this implicit treatment eliminates a numerical instability present with an explicit treatment. During this research, we have also observed that the approximate nonlinear solution converges slowly with the number of OL iterations. Furthermore, simulation results reveal: the existence of multiple solutions and occasional convergence failures of the nonlinear solver. For a time step comparable to the forcing time scale, a few OL iterations lead to errors in the velocity field that are of the same order of magnitude as the mean drift. The slow convergence is an issue at all spatial resolutions but is more severe as the grid is refined. It is attributed in part to the standard VP formulation that leads to a momentum equation that is not continuously differentiable. To obtain a smooth formulation, we replaced the standard viscous coefficient expression with capping by a hyperbolic tangent function. This provides a unique solution and reduces the com / Cette thése de doctorat présente le développement d'un modéle a haute résolution visco-plastique (VP) de la glace de mer. Etant donné le maillage fin utilisé et la taille du domaine, un schéma numérique efficace et parallélisable est souhaitable. En premier lieu, nous avons utilisé le solveur non linéaire utilisé dans les mod éles VP existants (appelé le solveur standard). Ce solveur non linéaire est basé sur un solveur linéaire et une boucle externe (BE). Comme solveur linéaire, nous avons appliqué la méthode du résidu minimal généralisé avec préconditionneur (pGMRES). Le préconditionneur est un solveur de surrelaxation successive (SOR) par ligne. En comparant avec les autres méthodes utilisées dans la communauté, nous avons constaté que pGMRES est 16 fois plus rapide qu'un solveur SOR et 3 fois plus rapide qu'un solveur SOR par ligne. Pour pGMRES, la symétrie de la matrice du systéme n'est pas requise. Le terme de Coriolis et la partie hors diagonale de la contrainte du vent peuvent donc etre traités implicitement. Des résultats théoriques et des simulations démontrent que ce traitement implicite élimine une instabilité qui peut etre présente dans le cas d'un traitement explicite. Au cours de cette recherche, nous avons aussi observé que la solution non linéaire approximée converge trés lentement avec le nombre d'itérations de la BE. De plus, des résultats de simulation montrent: l'existence de solutions multiples et des cas de non convergence du solveur non linéaire. Lorsque le pas de temps est comparable a l'échelle temporelle du forçage, un petit nombre d'itérations de la BE implique des erreurs sur les vitesses simulées du meme ordre de grandeur que la vitesse moyenne. La lente convergence est un probléme pour toutes les résolutions spatiales mais est plus sévére a haute résolution. Elle est attribuable entre autr

This thesis describes the variability and mean flow of the Subantarctic Front (SAF) south of Australia using time series measurements of velocity and temperature from 1993 to 1995, and six hydrographic transects along WOCE line SR3 from Tasmania to Antarctica over the period 1991 to 1996. The SAF is the strongest jet of the Antarctic Circumpolar Current (ACC) south of Australia. The time series of velocity and temperature are only the third such dataset collected in the ACC and provide insight into the dynamics of this massive current and into the heat and momentum balances of the Southern Ocean. The SAF was found to be an energetic, meandering jet with vertically coherent fluctuations. These fluctuations varied on a timescale of 20 days, and had a typical amplitude of 30 cm/s at 1150 dbar. The analysis used a coordinate frame that rotated daily to be in alignment with the direction of flow. This allowed the mesoscale variability of the SAF to be isolated from variability due to meandering of the front and proved very successful for examining eddy fluxes. Vertically averaged cross-stream eddy heat flux was 11.3 kW/m^2 poleward and was significantly different from zero at the 95% confidence level for fluctuations with periods between 2 and 90 days. Zonally integrated, this eddy heat flux (=0.9x10^15 W) is more than large enough to balance the heat lost south of the Polar Front and is as large as cross-SAF fluxes found in Drake Passage. Cross-stream eddy momentum fluxes were small and not significantly different from zero but were tending to decelerate the mean flow. A relationship between vertical motion and meander phase identified in the Gulf Stream was found to hold for the SAF. Eddy kinetic energy levels were similar to those in Drake Passage and southeast of New Zealand. Eddy potential energy was up to an order of magnitude larger than at the other ACC sites, most likely because meandering of the front is more common south of Australia. Baroclinic conversion was found to be the dominant mechanism by which eddies grow south of Australia. The typical time for the growth of an eddy is estimated to be 30 days, approximately half that in Drake Passage. This is consistent with observations from satellite altimetry which indicate that eddy energy is growing rapidly downstream of the Australian measurement site, while the eddy field in Drake Passage is mature. Mean cross-stream profiles of absolute and baroclinic velocity in the SAF at five current meter levels have been obtained from two streamwise profiling techniques using specific volume anomaly at 780 dbar as the cross-stream coordinate. One of the techniques, using hydrographic data to estimate the baroclinic velocity profile, is presented for the first time. The mean SAF velocity profile is composed of one central peak, reaching 52 and 34 cm/s at 420 dbar, absolute and baroclinic respectively, and several smaller peaks. The SAF flow is coherent at all levels, reaches the sea floor, and is at least 220 km wide. The cross-stream structure of baroclinic and absolute transport of the SAF has been characterized for the first time. The integrated mean transport is at least 116+/-10 x 10^6 m^3/s, of which approximately 14% is barotropic. The linear conditions for baroclinic and barotropic instability are satisfied at the array, consistent with the eddy growth rates calculated.

Thesis (Ph.D.)--University of Colorado at Boulder, 2007. / (UMI)AAI3273735. Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4347. Adviser: James W. C. White.

<p> The purpose of this thesis is to propose and develop a novel tool for measuring seafloor displacement using repeated sidescan sonar surveys, a data set that is collected alongside multibeam bathymetry. Chapter 1 presents the motivation for this study and introduces the work done in subsequent chapters. Chapter 2 is a brief overview of the design and underlying physics of the multibeam sonar, and presents a discussion on the uncertainties introduced by errors in the sound velocity profile. Chapter 3 presents the processing method for measuring seafloor displacement from sidescan sonar in detail, and tests this method by measuring synthetic displacements introduced into legacy multibeam data. Chapter 4 presents data collected in calibration surveys during the RR1605 and SR1704 cruises meant to test this method. We find displacements measurements with RMS uncertainties less than 0.5 m under optimal survey designs involving speeds less than 6 knots, kinematic post-processed ship navigation, and frequent measurements of the sound velocity profile. Chapter 5 demonstrates the improvement in ship positioning obtained when performing kinematic post-processing on the raw ship navigation data rather than relying on the real-time navigation solution.</p><p>

The Taupo Volcanic Zone (TVZ) is an area of extensive volcanism and geothermal activity in the North Island of New Zealand. The Calypso Hydrothermal Vent Field (CHVF) is located in an offshore extension of the TVZ on continental shelf, approximately 10 km southwest of the White Island subaerial volcano, at 180-200 m water depth in the Bay of Plenty, New Zealand. Active, moderate temperature (up to 201&deg;C) hydrothermal venting is contained within the Whakatane Graben, a northeast trending depression that has been partially filled by tephra from regional, subaerial volcanic eruptions. Venting of hydrothermal fluid through the volcaniclastic material has led to a varied and geographically distinct assemblage of alteration mineral phases in 4 vent fields in an area of approximately 50 km2. Carbon dioxide is the primary gas phase measured at active vent sites; sulfur is present as reduced H2S gas. The North Vent Field (NVF) is the original site of hydrothermal venting reported at Calypso. Weakly lithified volcaniclastic material recovered from this site has been altered primarily to montmorillonite, a dioctahedral smectite clay; minor mixed-layer clays were also detected. Native sulfur is spatially associated with the pervasively clay-altered samples, and is observed cementing volcaniclastic particles and filling primary pore spaces. Anhydrite mounds were also observed in the NVF. The principal hydrothermal alteration phase at the Southeast Vent Field (SEVF) and the Southwest Vent Field (SWVF) is amorphous silica which has filled the pore spaces between volcaniclastic particles and has overprinted early barite, minor clay, and native sulfur mineral phases. Cinnabar, stibnite, and amorphous arsenic sulfides form crusts on the outer surfaces of the samples as well as filling fractures, and forming inclusions within pyrite-silica veins. Textural relationships indicate volatile metal As, Sb, and Hg deposition is contemporaneous with silica precipitation. Clay-altered, sulfur-rich samples were also recovered from the Southeast and Southwest Vent Fields (SEVF, SWVF) but are volumetrically subordinate to the silica alteration facies. Several volcaniclastic samples from this site contained liquid hydrocarbon and charcoal fragments. A similar juxtaposition of alteration phases is observed in active geothermal environments in the subaerial portion of the TVZ (e.g., Waiotapu, Broadlands-Ohaaki). Where fluid conduits intersect the surface, near-neutral pH, chloride water will precipitate silica sinter with elevated volatile metal concentration +/- precious metals. Sinter deposits are characterized by a terraced morphology of opal precipitates and define the paleosurface in fossil epithermal systems. Such deposits have not been reported in the submarine environment. However, locations with high silica concentration, "sinter-like" material, and anomalous Hg-Sb-As concentrations have been described. At the Calypso field volcaniclastic material is cemented by amorphous silica similar to the silicified stratigraphy observed below silica sinter in some fossil epithermal deposits. The CO2 and H2S gas present in the hydrothermal fluid rise to areas of elevated topography peripheral to the sinter. Mixing of CO2 with water creates carbonic acid, and oxidation of H 2S may produce native sulfur and sulfuric acid; the extent of these reactions is limited by the availability of oxygen. In subaerial epithermal systems, the formation of sulfuric acid, and in turn advanced argillic steam-heated alteration, is limited to the vadose zone, where there is sufficient oxygen to produce sulfuric acid. In the absence of atmospheric oxygen, the production of sulfuric acid in submarine environments is similarly limited, and this explains the absence of aluminous clay minerals and alunite in the Calypso samples. Disproportionation of SO2(g) to H2SO4 (aq) does, however, create advanced argillic alteration in some higher-temperature submarine volcanic-hydrothermal systems (e.g., Brothers Volcano, de Ronde et al., 2005).